The present disclosure relates to a multi-layer electrode system and a method for producing a multi-layer electrode system, to a corresponding apparatus and also to a corresponding computer program product.
Piezoelectrical materials have the particular characteristic that when an electrical field is applied, said materials either expand or contract, or rather as an inverse effect an electrical field is produced as soon as the material is caused to expand or shrink. Piezoelectrical materials are used in actuator technology in order to develop highly precise positioners. By way of example, a PZT actuator can be used in order to operate a gyroscope. Piezoelectrical materials provide an elegant option for a sensor to convert the smallest length changes directly into an electrical signal.
Finally, piezoelectrical materials are widely used in micro-energy harvesters. In this case, mainly accelerations in the form of vibrations are converted into electrical energy.
There are currently two different approaches available for producing piezoelectrical elements in multi-layers. In a first method, piezoelectrical multi-layers are generated using thick-film technology. The multi-layers are configured in such a manner that in each case one layer of piezoelectrical material lies between two respective layers of electrodes. Since the piezoelectrical effect depends upon the electrical field, the necessary applied electrical voltage can be divided by the number of individual layers. The voltage is applied in such a manner that one half of the electrode layers in other words each second electrode layer is connected to the other half. The electrodes contact a multi-layer component by way of a thick-film structuring during the electrode deposition and a metallization of the end surface of the multi-layer component. The thinnest layers that can be achieved in the thick film are approximately 20 μm, wherein the PZT when using the thick-film technology has breakdown field strength of approx. 2 V/μm. This means that voltages of approx. 40 V are required in order to work with field strengths in the region of the breakdown and this result in the largest mechanical adjusting paths.
The thin-film technology used in microsystems technology mainly only renders it possible to use a single layer that has only one piezoelectrical layer. Two different methods are available for the deposition of the piezoelectrical material, on the one hand an application process based on sol gel or on the other to perform the deposition process in a vacuum. The layer thicknesses that are created using these methods are a few 100 nm up to 10 μm. As a result of the higher quality of the thin layers, the breakdown strengths are approx. 10 V/μm. Consequently, voltages of up to 10 V at a layer thickness of 1 μm are sufficient in order to work at the limit up to the breakdown. It is of advantage particularly when performing the deposition process in a vacuum that alternating electrode material and piezoelectrical material can be deposited in one machine in one process and it is possible as a result to create multi-layers.
One known approach for producing an electrical contact is to make contact with individual electrodes in an alternating manner. In so doing, each electrode is structured individually calibrated in a photolithographical manner. For a technically expedient implementation, it is possible using this method to produce a multi-layer that has up to five layers.
A further option provides a movable shadow mask. In this case, when performing the electrode deposition process in a vacuum, a hard mask is moved across the substrate, and the electrode is only deposited in open regions of the mask. The mask is removed for the subsequent piezoelectrical deposition and re-positioned in an offset manner when depositing the next electrode.
US 2011/0294015 A1 describes a method for producing a thin-film battery. A first electrode material, a battery material and a second electrode material are repeatedly deposited one after another on a carrier structure without using a mask in order to form a thin-film battery that has a plurality of first electrode layers, battery layers and second electrode layers.